Instead, the whole thing should be pushed back to those that are paying the "shit posters". They're the ones that should be policing the posts and not paying shit posters. Then your crew could review the posters of various campaigns and if they find the campaign is not policing the posts adequately, they lose their sig campaign privileges for some period of time. Just a thought off the top of my head.
Negative trust only does so much. I'm not disagreeing with you, I just like playing the devil's advocate on these issues.
See: Betcoin.ag (campaign and site)
People stuck with that signature campaign well after it was revealed to be a scam site with plenty of other shady activity.